The present invention relates generally to photographic media, and, more particularly, to an apparatus and method for applying a lubricant coating over a magnetic coating on a web.
A magnetic recording layer is included in the composition of photographic film for recording identification data or other data. The magnetic layer is coated with a lubricating layer which protects the magnetic recording layer and allows the films to be thrust in and out of a film cartridge without damage. Photographic film is typically constructed by building the various layers on a substrate using transport rollers during the manufacture to move the substrate as a web from one layering station to the next. Because the total thickness of the layered film is on the order of 0.004 inch (0.1 mm), each layer is extremely thin, and must be applied carefully to maintain uniformity and prevent over spray or splattering. One process for applying a thin layer of material to a substrate is vacuum vapor deposition. It is desirable to use a vapor deposition process to apply a thin, uniform lubricating layer. A problem with vapor deposition is that the vapor cloud can collect on surfaces other than the magnetic layer thereby contaminating the film. It is therefore desirable to have an apparatus that prevents free vapor from contaminating the web or vacuum chamber.
According to one aspect of the present invention, a lubricant deposition station coats a lubricant onto the back side of a moving web of photographic film prior to coating the front side with emulsions. The deposition station has a sidewall creating a chamber containing a heat source along its bottom and an evaporating tray above the heater which holds the lubricant material to be vacuum vapor deposited on the film. The web is threaded through the system such that the back or target side of the web is exposed to the open tray of heated lubricant material while being transported through the vacuum deposited lubricant station. A water cooled jacket fits about the top of the sidewall and receives the film through a narrow slot between its top and bottom plates to expose the back side of the film to a vapor cloud of lubricant in the deposition station. Lubricant from the vapor cloud deposits on the back side of the film. Stray lubricant from the cloud condenses on the bottom plate which receives cooling water through an inlet. The cooling water traverses the length of the bottom plate, enters the top plate through a water loop connecting the top and bottom plates, and exits through the top plate. The vapor cloud condenses on the bottom plate without reaching the front side of the film.